Telephone-exchange system.



W. H. HARRISON. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY 9. 1918.

Patented Dec. 10, 1918.

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WILLIAM H. HARRISON, OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCOR?ORATED, OF N EVJ YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed May 9, 1918.

To all iv/1.0772, it may concern:

Be it known that I, WILLIAM H. HARRI- SON, a citizen of the UnitedStates, residing at Brooklyn, in the county of Kings, State of New York,have invented certain new and useful improvements in Telephone-EX-change Systems, of which the following is a full, clear, concise, andexact description.

This invention relates to telephone exchange systems, and moreparticularly to such systems employing trunkcircuits over whichconnections between telephone "lines terminating at differentswitchboards may be made.

The object of this invention is to provideimproved signaling means forsystems of,

, this invention, reference should be had to the following description,considered in connection with the accompanying drawing illustrating oneembodiment thereof.

As shown in the drawing, a trunk circuit A extends from a firstswitchboard X to a second switchboard Y. At the switch board X there islocated a cord circuit B, by means of which connection may be madebetween a telephone line (not shown) terminatin at switchboard X and thetrunk circuit A. A cord circuit C provided at the switchboard Y may beemployed for connecting the trunk circuit A with an exten sion linerepresented by the jack D, or with a trunk circuit (represented by jack11) extending to a central office. The extension telephone line D andthe trunk circuit E are preferably of the types disclosed in the patentto H. L. Darrah, No. 1,232,5OZ, with this difference, that the sleevecontactof the jack of the extension line D has no ground connection andthe sleeve contact of the 1 Specification of Letters Patent.

Patented Dec. 10, 1918.

Serial No. 233,449.

jack of the trunk circuit E has a ground instead of a batteryconnection.

The cord circuit C may also be employed to interconnect extension linesor to connect an extension line with the central oflice trunk circuit.The apparatus shown to the left of the dotted line, 22, may be locatedat the switchboard X, and that shown to the right of the dotted line3-3, at the switchboard Y.

The. operator at switchboard X desiring to establish a connection withor through the switchboard Y may insert plug 5 of the cord circuit Binto jack 6 of the trunk circuit A, whereupon lamp 7 is lighted andrelay 8 operated over a circuit from battery through the normal contactof the listening key 9, contact of supervisory relay 10, lamp 7, sleevecontacts of the plug 5 and the jack 6 and the winding of relay 8 toground. Relay 8, in operating, causes the operation of a slow-releaserelay 11, the function of which will more fully hereinafter appear.Relay 12 also operates upon the connection of the plug 5 with the jack6. The operator may now actuate ringing key 13 to cause the operation ofrelay 15 over a circuit from a source of ringing current 16 through thelower alternate contact of ringing key 13,

ring contacts of the plug 5 and the jack 6, condenser17, winding ofrelay 15, tip contacts of the jack 6 and'the plug 5, contact of relay 12and the upper alternate contact of ringing key 13 to ground. Relay 15,in operating, causes the operation of relay 18, which connects a secondsource of ringing current 19 in circuit with and operates anelectromagnetic drop 20, the shutter 21 of which falls to furnish asignal. The restoration of the ringing key 13 to normal position causesthe release of relays 15 and 18 and the disconnection of the source 19from the trunk circuit. The operator at switchboard Y, observing theoperated condition of the drop 20, may insert plug 30 of the cordcircuit G into jack 31 of the trunk circuit A, where upon a slow-releaserelay 32 operates over a circuit from batterv through the winding ofrelay 32 and local contact 33 of the jack 31. After inserting the pluginto the jack, the operator may restore the shutter 21 of the drop toits normal position. Relay 34 of the cord circuit C, and relay 35 of theLit) trunk circuit Ado not operate. Relay 32, in operating, connects amarginal relay 36 inbridge of the trunk circuit A, and establishes ashort circuit about the winding of the drop 20. This short circuit maybe traced from the point 37 through the normal contact of theslow-release relay 38 and contact 39 of relay 32 to the point 40. Thedrop 20, by being short-circuited, is thereby operatively disconnectedfrom the trunk circuit, and is prevented from operating after itsshutter has been restored by the operator. \Vith this short circuitabout the drop, .the drop is not operated by currents induced in theleft-hand windings of repeating coil 41,

resulting from the closure and opening of circuit including theright-hand windings of this repeating coil.

The connection of the marginal relay 36 in bridge of the trunk circuitcauses. the operation of a trunk relay 42 over a circuit from batterythrough the lower right-hand winding of repeating coil 43, lower normalcontact of relay 18, lower left-hand winding of repeating coil 41,winding of-relay 36, contact 44 of relay 32, upper left-hand winding ofrepeating coil 41, upper normal contact of relay 18, upper right-handwinding of repeating coil 43 and both windings of relay 42 to ground.Trunk relay 42, in operating, causes the operation of relay 45, whichconnects relay 46 in bridge of that end of the trunk circuit whichterminates at. the switchboard Y. Supervisory relay 10 isthereuponoperated over a circuit from battery through the lower windingof" re tardation coil 48, winding of supervisory relay 10, lower normalcontact of ringing key 13, ring contacts of the plug and the jack 6,lower left-hand winding o'f repeating coil '43, lower contact of relay45, winding of relay 46, upper contact of relay 45 and the normalcontact of relay 46 to ground. Supervisory relay 10, in operating,causes the efiacement of the supervisory lamp 7 which mayselve as asignal to the originating operator that the distant operator hasanswered. The operator at switchboard X may then actuate listening key 9to connect the telephone set with the cord circuit B. Relay 46 alsooperates, establishing a short circuit for the lower winding of re lay42, thereby reducing the resistance in circuit with themarginal relay 36which now operates. Upon the operation of relay 46, the energizing pathfor relays and 46 from the point 22 then continues to ground by way ofthe upper left-hand winding of repeating coil 43, tip contacts of thejack 6 and the plug 5, the contact of relay 12, upper normal contact ofringing key 13 and the upper winding of retardation coil 48. Relay 36,in operating, establishes operating circuits for slow-release relay 38and lockup relay 50. Relay 50, in operating, establishes a lockingcircuit for itself from batincluded in shunt of the winding of the dropThis resistance is low enough to prevent the operation of the drop uponthe discharge of either of the condensers 24 or 25. The drop, therefore,remains operatively disconnected from the trunk circuit.

The operator at switchboard Y may now actuate listening key 51 toconnect the operators telephone set with the trunk circuit. Since theoperators telephone set at the switchboard X .is already connected incircuit, the two operators may converse. It connection is to beestablished with an extension line, the operator at switchboard Y mayinsert plug 52 into the jack D, and may then actuate a ringing key (notshown) to connect with the extension line ringing current for operatingthe usual call bell. .Upon response of the subscriber on an extensionline, the line circuit is closed in the usual manner, whereupon theannunciator is actuated to furnish a signal indicating to the operatorthat the subscriber has respond ed. This annunciator 53 furnishes asignal while the subscribers are talking, and does notdisplay'a signalwhen the subscriber has restored the receiver to the switchhook.

If connection is to be established with a line terminating at a centraloflice (not shown) the operator at switchboard Y may then insert theplug 52 into the jack E, whereupon relays 34 and operate in parallel byway of the grounded sleeve contact of the jack of trunk circuit E. Theopera- 'tion of these two relays disconnects battery for talkingpurposes from both the trunk and the cord circuit. As is usual whenconnectlon 1S established over a central office trunk circuit between aprivate branch eX- change telephone line and a central oiiice telephoneline, battery for talking purposes is furnished from the central otlice.The operation of relay 34- connects retardation coil 54 in bridge of thetalking strands of the cord circuit, and relay 35, in operating,connects a resistance 55 in bridge of the talking conductors of thetrunk circuit, thereby establishing a circuit for the usual line relayconnected with the central oiiice end of the trunk circuit.

If the operator at switchboard Y, after inserting plug 30 into the jack31, does not operate the listening key 51, the operator at switchboard Ymay desire to re-ring the operator at switchboard Y. This may be done bywithdrawing the plug 5 from, and then reinserting it in, the jack 6.Upon the withdrawal of the plug from the jack, relay 46 releases itsarmature, thereby opening the short circuit about the lower winding ofrelay 42. The resistance in circuit'with marginal relay 36 is therebyincreased, causing the release of this relay'36- Upon the release ofrelay 36, the drop 20' isenergized over a circuit from battery throughthe leftf hand lower winding of repeating coil 43,

lower normal contact of relay l8 and lower left hand winding of Irepeating coil .41, winding of the drop 20, alternate contact ofslow-release relay 38, left-hand alternate contactof relay 50, normalcontact of relay 36 and contact 33 to ground. The energiza? tion of drop20 causes the attraction of the armature of the drop, .which' releasesthe shutter 21 to furnish a signal. The closure of this operatingcircuit of this drop20 but momentary, for relay38, which is oftheslow-release type, begins to release its armae ture immediately upon therelease" of the marginal relay 36. U on the withdrawal of the plug 5from the jack 6, relay 8 is deenergized, and relay 26 is energized overa.

path from battery through the normal contact of relay 8, winding ofrelay 26, .normally closed cont-act of the jack 6, upper left-handwinding of the repeating coil 43, upper contact of relay 45 and thenormal contact of relay 46 to ground, Since relay 11 is of theslow-release type, the lower contact of relay 26 is closed before thelower alternate contact of relay 11 is opened, whereby a locking circuitfor relay 11 is completed. The lighting of the lamp27 to furnish a falsesignal is thereby prevented. The reinsertion of the plug 5. within thejack 6 causes the energizati'on of relay 46,

from the jack 6 causes the deenergization of relays 8 and 46, and theenergization of relay 26. causes marginal relay 36 to release itsarmature, as before described, ,to momentarily close an. operatingcircuit for the drop 20, which permits its shutter 21 to fall to displaya disconnect signal. This shutter 21 may be restored to its normalposition be.- fore the operator at the switchboard Y withdraws the plug30. from the jack 31. In withdrawing the plug 30 from the jack 31,condenser 28 may be discharged, or a battery circuit including theright-hand windings of repeating coil 41 may be opened or closed. Ineither event, the resulting flow of The deenergization of relay 46vcurrent through the repeating coil windings induces a current in theleft-hand wmdings thereof, whereuponthe condensers 24 and 25 maydischarge. The drop 20, therefore, remains operatively disconnected fromthe trunk circuit until after the condensers have been discharged, inorderthat there may be no false operation of the drop; The

operative'disconnection of the drop 20 from the trunk circuit is thusmaintained, due to slow-release relay 32, which, for an a preciable timeafter the disconnection o the plug from the jack, holds closed the shuntcircuit has assumed its normal condition.

Should a call originate atthe switchboard Y and connection forcompletion over the. trunk circuit A, the insertion of the plug 30 intothe jack 31 causes the operation of relay 32. Relay 36 is therebybridged across the talking strands of the trunk circuit, whereupon relay42 operates over a circuit from battery through the lower right-handwinding :of repeating coil 43, lower normal contact of relay 18, lowerleft-hand winding of repeating coil 41, winding of relay 36, contact 44of relay 32, upper left-hand wind.- ing of repeating coil 41, uppernormal contact'o'f relay 18, upper right-hand winding of repeating coil43 and the two windings of relay 42 to ground. Relay42, upon op erating,causes thev energization of relay 45. Upon being energized, relay45tcauses, the

operation of relay 26 overa circuit from bat tery through the normalcontact of relay 8, winding of relay 26, normally closed contact of thejack 6, upper left-hand winding of repeating coil 43, upper contact ofrelay 45 and the normal contact, of relay 46 to groundf Relay 26, inoperating, completes a circuit over which the lamp 27 is lighted, tofurnish a signal to the operator at the switchboard X.

The operator at the switchboard X, upon observing the lighted conditionof the lamp 27, inserts theplug 5 into the jack 6, where upon relay 8operates and relay 26 releases,

eflacing the lamp 27. Relay 8, in operating,

causes the operation of slow-release relay 11 as beforedescribed. Relay46 now operates and short-circuits the lower winding of relay 42,thereby permitting the operation of relay 36. Relay 36, in operating,causes the operation of slow-release relay 38 and lockup relay 50. Thelatter, in operating, closes a locking circuit for itself through itsrighthand alternate contact and contact 33 of'the v jack31.

forethe other operator, thev withdrawal of the plug 30: from the-jack 31causes the re -i leaseof relays 32,38, 50, andfl2. Relay 42, inreleasing, causes the release. of relay 4L5'followed by the release ofrelays l6 and e 10, whereupon thesupervisory lamp 7 lights to furnishadisconnect signal to the opera;

' tor at switchboard X, a Since relay 38zisnow released and itsalternate contact is open,

therewill be no. false operation of the drop 20 upon the withdrawalof;the plug 5 from the jack 6. I g a What isclaimed'is; k e a a l; Atelephone exchange systemcomprising a trunk circuit extending from afirst to a second switchboard, a link circuit at the, first switchboardconnected with the trunk circuit, a signaling device at the secondswitchboard normally. operatively asso ciated with the trunk circuit, asource ofsignalingcurrent, means in the link circuit for connecting thesource of signaling current withthe trunk circuit for causing theoperation of the signalingdevice, a link circuit at the secondswitchboard, means responsive to the connection of the second link circli. with the trunk circuit for operaa tively disconnecting the signalingdevice therefrom, and,v means responsive to, the disconnectlon of the,first link circu t from the trunk circuit for operatively associatingthesignaling devicewith the trunk circuit and for causing theoperationthereof.

2. A telephone exchange system comprising a trunk. circuit extendingfrom a first to a second switchboard, a link circuit at the firstswitchboard connected with the trunk circuit, a signaling deviceat thesecond switchboard normally operatively associated with the trunkclrcult, a source of signaling current, means in the trunk circuit forconnecting the source ofsignaling current with the trunk circuit forcausing the operation of the signaling device, a link circuit atthesecondswitchboard, a normally open shunt circuit for the signalingdevice,

a relay energized upon the connection of the second link circuit withthe trunk circuit for establishing the shunt circuit about the signalingdevice, and a relayresponsive to the disconnection of the first linkcircuit from the trunk circuitfor, completing an operating circuitthroughcthe signaling device. a

3. A telephone exchange system comprising a two-conductor trunk circuitextending from a first to a second switchboard, a link circuit atthefirst switchboard connected withthe trunk circuit, a signaling device atthe second switchboard normally operatively associated with the trunkcircuit, a source of signaling current, means in the link circuit forcontrolling the connection of the source of signaling current in circuitwith the two conductors of the trunk circuit and the signaling devicethereby to operate the signaling device, a link circuit at the secondswitchboard, an operating circuit for the signaling device including oneof the conductors of; the trunk circuit, means responsive to theconnection of the second link circuit with the trunk circuit forpartially establishing the operating circuit, and means responsive tothe disconnection of the first link circuit from the trunk circuit forcompleting the partially established operating circuit;

4. A telephone exchange system comprising a two-conductor trunk circuitextending from a first to. a second switchboard, alink circuit at thefirst switchboard connected withthe trunk circuit, a signaling device atthe second switchboard normally operatively associated with the trunkcircuit, a source of signaling current, means in the link circuit forcontrolling the connection of the source of signaling current in circuitwith the two conductors of the trunk circuit and the signaling devicethereby to operate the signaling};v device, a link circuit at the secondswitchboard, a relay energized upon the connection of the second linkcircuit with the trunkcircuit, a second relay bridged across thetwoconductorsof the trunk circuit upon the energization of the first, relayand operating thereover, a slow-release relay energized upon theoperation of the bridged relay, a relay in the trunk circuit responsiveto the disconnection of the first link circuit from the trunk circuitfor causing the release of the second relay, and an operating circuitfor the signaling device completed upon the release of the second relayand including a contact of the slow-release relay.

5 A telephone exchange system comprising a two-conductor trunk circuitextending from a, first to a second switchboard, a link circuit at thefirst switchboard connected with the trunk circuit, a signaling deviceat the second switchboard normally operatively associated with the trunkcircuit, a source of signaling current, means in the link circuit forcontrolling the connection of the source of signaling current in circuitwith the two conductors of the trunk circuit and the signaling devicethereby to operate the signal-, ing device, a link circuit at the secondswitchboard, an operating circuit for the signaling device including oneof the conductors of the trunk circuit, a relay in the trunk circuitresponsive to the connection of the second link circuit therewith forpartially establishing the operating circuit, and a relay responsive tothe disconnection of the first link circuit from the trunk circuit forcompleting the operating circuit.

6. A telephone exchange system comprising a trunk circuit extending froma first to a second switchboard, a source of signaling current at thefirst switchboard, means there at for connecting the source of signalingcurrent with the trunk circuit, a signaling device in the trunk circuitresponsive to the connection of signaling current therewith, a linkcircuit at the second switchboarch means in the trunk circuit responsiveto the connection of the link circuit therewith for open ativelydisconnecting the signaling device from the trunk circuit, and switchingmeans responsive to the opening of the trunk circuit at the firstswitchboard and cooperating with the second mentioned means for causingthe operation of the signaling device.

7. A telephone exchange system comprising a trunk circuit extending froma first to a second switchboard, a link circuit at the first switchboardconnected with the trunk circuit, a signaling device at the secondswitchboard, a source of alternating current, means in the link circuitcontrolling the connection of the source of alternating current with thetrunk circuit for operating the signaling device, a link circuit at thesecond switchboard, means responsive to the connection of the secondlink circuit with the trunk circuit. for rendering the signaling devicenon-responsive to alternating current, a source of direct current, andmeans responsive to the disconnection of the first link circuit from thetrunk circuit for connecting the source of direct current in circuitwith the signaling device.

8. A telephone exchange system comprising a trunk circuit extending froma first to a second switchboard, a link circuit at the first switchboardconnected with the trunk circuit, a signaling device at the secondswitchboard, a source of alternating current, means in the link circuitcontrolling the connection of the source of alternating current with thetrunk circuit for operating the signaling device, a link circuit at thesecond switchboard, a relay in the trunk circuit responsive to theconnection of a second link circuit therewith for rendering thesignallng device non-responsive to alternating current, a source ofdirect current, and a relay responsive to the disconnection of the firstlink circuit from the trunk circuit for connecting the source of directcurrent in circuit with the signaling device to cause the operationthereof.

, 9. A telephone exchange system comprising a trunk'circuit extendingfrom a first to a second switchboard, a link circuit at the firstswitchboard connected with the trunk circuit, a signaling device at thesecond switchboard, a source of alternating current, means in the linkcircuit controlling the connection of the source of alternating currentwith the trunk circuit for operating the signaling device, a linkcircuit atthe second switchboard, a relay in the trunk c'ircuitresponsive to the connection of the second link circuit therewith, asource of direct current, a relay responsive to the disconnec tion ofthe first link circuit from the trunk circuit, and an operating circuitfor the sig naling device and a source of direct current establishedupon the response of the second relay and including contacts of bothrelays.

10. A telephone exchange system comprising a trunk circuit extendingfrom a first to a second switchboard, a link circuit at the firstswitchboard connected with the trunk circuit, a signaling device at thesecond switchboard, two sources of current of different character, meansin the link circuit controlling the connection of one of the sources ofcurrent with the trunk circuit for operating the signaling device, alink circuit at the second switchboard, means responsive to theconnection of the second link circuit with the trunk circuit foroperatively disconnecting the signaling device from the trunk circuit.and means responsive to the disconnection of the first link circuit fromthe trunk circuit for connecting the other source of current in circuitwith the signaling device.

11. A telephone exchange system comprising a trunk circuit extendingfrom a first to a second switchboard, a link circuit at the firstswitchboard connected with the trunk circuit, a signaling device at thesecond switchboard, two sources of current of different character, meansin the link circuit controlling the connection of one of the sources ofcurrent with the trunk circuit for operating the signaling device, alink circuit at the second switchboard, means responsive to theconnection of the second link circuit with the trunk circuit, a normallyineffective operating circuit for the signaling device and the other ofthe two sources of current, and means responsive to the disconnection ofthe first link circuit from the trunk circuit and cooperating with theother responsive means to render the operating circuit effective forcausing the operation of the signaling device.

12. A telephone exchange system comprising a trunk circuit extendingfrom a first to a second switchboard, a link circuit at the firstswitchboard connected with the trunk circuit, a signaling device at thesec- 0nd switchboard, two sources of current of different character,means in the link circuit controlling the connection of one of thesources of current with the trunk circuit for operating the signalingdevice, a link circuit at the second switchboard, a relay energizedWhile the second link circuit is connected with the trunk circuit, arelay dot-Energized upon the disconnection of the first link circuitfrom the trunk circuit, and an operat- 10 In Witness whereof, I hereuntosubscribe 15 my name this 3rd day of May A. D., 1918.

VVILLIAM H. HARRISON.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. 0.

